HYDRODYNAMICS OF SEMIBATCH SLURRY BUBBLE-COLUMNS WITH POLYMER-SOLUTIONS

In this work we perform an experimental study of the hydrodynamics of semibatch slurry bubble columns in which the liquid phase is a solutio n of a high molecular weight hydrolyzed polyacrylamide. Experiments we re conducted in bubble columns with two different diameters (10 and 29 cm.) In gas-liquid operation, the gas holdup decreases as the polymer concentration increases due to the formation of large stable bubbles. In the presence of high solids concentration, this trend is reversed in the larger column due to an increase in the number of small bubbles and an appreciable increase in the residence times of the large bubbl es brought about by an increase in slurry circulation. The distributio n of solid phase becomes more uniform as the polymer concentration inc reases. This trend is quantified by means of the application of a modi fied form of the sedimentation-dispersion model. The macromolecular co nformation of the polymer in solution is altered by adding NaCl, whose positive ions screen negative charges in the polymer molecule produci ng a contraction of the coil. At the concentration levels used in this work, the addition of salt decreases the ability of the polymer to pr oduce a more uniform solids distribution.